This invention generally concerns wireless communications and, more particularly, a system and method for assigning a Packet Data Serving Node (PDSN) to a wireless mobile station (MS), to provide packet data services in a third-generation (3G) code division multiple access (CDMA) communication system.
In the second generation CDMA systems specified by the IS-95B standard, uplink data bursts from a MS to base station are limited to a small number of frames, typically 8 or less. The data rate is limited to 4.8 kbps, i.e., inferior to the one used by the users active on the dedicated (voice) channels, which is 9.6 or 14.4 kilobits per second (kbps). The 3G CDMA, as described in IS-2000 body of standards, is being designed to accommodate both longer messages (more frames per message) and higher data rates to support the communication packetized data. Data rates of 384 kbps are envisioned. The ability of the 3G CDMA to communicate packet data will permit users to seamlessly access the Internet with a computer through a wireless telephone.
The transfer of large volumes of data between the MS and the PDSN portal to the Internet will be aided by changing the 3G CDMA system from the traditional PSTN circuit-switched system, where the data network communication must be routed through the mobile switching center (MSC), to a system where the PDSN can locally connect to a radio access network (RAN) base station controller (BSC) using frame relay, or some other link-layer transport capable of carrying Internet protocol (IP) data packets. The linkage between the wireless system and the Internet can be more peer-to-peer and, therefore, simpler and faster, if the packet data protocol can be maintained across the PDSN.
FIG. 1 illustrates the architecture for the 3G CDMA radio access network (RAN), prior art. The packet control function (PCF) and PDSN are two new entities defined by the third-generation Partnership Project 2 (3GPP2) and are only relevant to packet data calls. The cardinality of PDSN and PCF association is many-to-many, meaning that it will be typical for many PCFs to be connected to each PDSN. Likewise, it will be typical for many PDSNs to be connected to each PCF.
When a packet data call is first established, by an MS request for example, a BS and associated BSC are selected as elements in the link. Typically, the BSC is associated with a particular PCF, which may even be co-located at the BS. The PCF must be connected to a PDSN, or a PDSN must be (initially) selected for the MS. There is currently no IS-2000 standard for the initial PDSN assignment.
Furthermore, the packet data link between the MS and PDSN, once initially selected, may become dormant as the MS ceases to communicate packet data. In this situation the air interface traffic and control channels are released, but the point-to-point (PPP) connection between the PDSN and the MS are maintained. It is foreseeable that a dormant MS will roam. Regardless of the relationship between PCFs and BCSs, a dormant MS will roam to a different packet zone (i.e. a new PCF). The new PCF must be notified and it must then establish a new connection to one of the PDSNs. It is highly desirable that the new PCF selects the PDSN that was previously selected by the old PCF. In this manner, the overhead required to reestablish a PPP connection can be minimized, even as dormant handoff occurs between the old and new PCFs, where the previous PDSN already has the PPP connection.
The current 3G CDMA network architecture does not have an interface or a mechanism defined to inform the new PCF of the PDSN which was previously selected by the old PCF, nor is there a third entity that overlooks all resources in the entire network.
In would be advantageous if there was a way for the same PDSN to be selected for packet data communications to a MS in the dormant state, in the event that a new PCF must be selected.
It would be advantageous if the same PDSN could be selected in a MS dormant state reselection process using the existing network architecture.
It would be advantageous if the same PDSN could be selected in a MS dormant state reselection process without the PCF and PDSN units having special knowledge of each other, without special network communications, or without the use of an independent network entity to control dormant state reselections.